Temporal variation in feeding rhythms in a tidal marsh population of the common goby Pomatoschistus microps (Kroyer, 1838)

Abstract.

Pomatoschistus microps (Teleostei, Gobiidae) intensively uses the mesohaline marsh of Westerschelde estuary as a nursery and foraging ground. The sampling campaign covered the semi-lunar, diel and tidal cycles. The density of P. microps and potential hyperbenthic prey species in the marsh creek, fullness index, evacuation rates and daily ration of common goby were calculated. Mesopodopsis slabberi, Neomysis integer and Corophium volutator were the most dominant prey items in terms of biomass. Numerically, copepods dominated the diet. Migrating fish enter the marsh creek with a relatively empty stomach and leave the marsh with a higher stomach content. Pomatoschistus microps seemed to feed more intensively during the day than the night, however the influence of the diel cycle is inferior in comparison with the tidal influence on the feeding behaviour of the common goby. A significant difference in foraging activity occurred between the spring and neap tide. The common goby migrated in lower abundance into the creek during spring tide but foraged more intensively. At both spring and neap tide, a significant difference was found in the fullness index between day and night. At spring tide, gobies feed more during the day, while they forage more intensively at night at neap tide. All the three cycles (tidal, diel and semi-lunar) influenced the feeding rhythm of the common goby. The tidal influence is superior over the diel variation, while the explanation of the combined effect of diel and semi-lunar cycle needs further studies.